JP3060117B2 - Compact 3-group zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small zoom lens suitable for a lens shutter camera or the like and having a zoom ratio of about 2 and a short overall lens length. It relates to a zoom lens.

[0002]

2. Description of the Related Art In recent years, as the zooming of lens shutter cameras has progressed, a more compact and lightweight zoom lens has been desired. In a lens system used for such a lens shutter camera, it is not necessary to secure a specific back focus unlike a lens system mounted on a single-lens reflex camera. However, if the back focus is too short, the diameter of the lens on the image side increases. Further, when the back focus is lengthened, the overall length of the lens is lengthened, and as a result, a compact small zoom lens cannot be formed.

For example, a lens system disclosed in Japanese Patent Application Laid-Open No. 62-78522 has a first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. In this conventional example, the telephoto ratio at the wide (wide angle) end is about 1.3, which is similar to that of a two-unit zoom lens, but the lens diameter of the first unit is large. large. In this case, the zoom ratio is about 1.5. As a conventional example in which the zoom ratio is about 2, and the same positive, positive, and negative refractive power distributions are provided, and the first and third units are integrated when zooming, And JP-A-2-501
No. 17 is available. In these conventional examples, the telephoto ratio at the wide end is as large as about 1.4 and 1.5, respectively. Also,
The overall length of the lens is long, and the lens diameter of the first group is also large.

[0004]

In the above-mentioned prior art, Japanese Patent Laid-Open No. 62-78522, the telephoto ratio at the wide end is 1.
Although it is about the same size as a two-unit zoom type with about three, and the overall length is short, the lens diameter of the first unit is large, which is disadvantageous for mounting the camera on a compact camera body. Japanese Patent Application Laid-Open No. 1-937, which is a prior example in which the first and third units move integrally to the object side during zooming at the same zoom ratio of about 2 as in the present invention.
No. 13 and JP-A-2-50117 have large telephoto ratios at the wide end of about 1.4 and 1.5, respectively, and have a long overall length. In addition, the first group has a large lens diameter and cannot be said to be a compact and compact zoom lens.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a wide-angle zoom lens of a three-group type having a zoom ratio of about 2. Shorten the telephoto ratio at the end to 1.3 or less, and
An object of the present invention is to provide a small zoom lens having a small first lens group diameter.

[0006]

As shown in FIGS. 1 to 4, a compact three-unit zoom lens according to the present invention that achieves the above object has a first group G1 having a positive refracting power, a A second group G2 having a refractive power and a third group G3 having a negative refractive power;
A three-unit zoom lens in which, during zooming from the wide-angle end to the telephoto end, the first and third units move toward the object side, and the second unit moves toward the object side at a relatively slow speed. The following conditional expressions (1) to (4) are satisfied.

(1) 0.5 <| f ₃ / f _W | <0.9 (2) 1.3 <β _3W <2.0 (3) 1.7 <f ₁ / f _W <5.0 (4) 0.5 <f ₂ / f _W <1.3 (5) 0.1 <E _W / f _W ≦ 0.237 where f _W is the focal length of the entire system at the wide-angle end, f ₁ ,
f ₂ and f ₃ are the focal lengths of the first, second and third lens _{units respectively} , β _3W is the imaging magnification of the third lens unit at the wide angle end, and E _W is the entrance pupil position from the first lens surface at the wide angle end. Is the distance to

[0008]

In the zoom lens according to the present invention, since the first group G1 and the second group G2 are closest to each other at the wide-angle end, a so-called telephoto type lens is constituted by the first group G1 and the third group G3. Therefore, by strongly setting the combined power of the first group G1 and the second group G2 and the power of the third group G3,
The total length of the lens can be reduced, and the conditional expressions set for that purpose are expressions (1) and (2).

If the power of the third lens unit G3 is weakened beyond the upper limit of the expression (1), the effect of the telephoto type is weakened, and the overall length of the lens becomes too long, making it difficult to shorten the overall length. If the lower limit is exceeded, it is advantageous for shortening the overall length of the lens, but the power of the third lens unit G3 is too strong, and it becomes difficult to correct aberration fluctuations, especially curvature of field.

[0010] (2) is a condition related to the imaging magnification of the third lens unit, if the first group G1 and the composite focal length of the second lens group G2 at the wide end and f _12W, f _W = f _12W Since β is _3W , equation (2) also defines the combined power of the first group G1 and the second group G2. When considering only shortening the overall length of the lens, for example, the back focus can be easily achieved by approaching 0.
Since the group G3 is too close to the image plane, its lens diameter naturally becomes large, which is not desirable for making the camera body compact. Therefore, even if the overall length of the lens is shortened, the effect of downsizing can be obtained only when a sufficient back focus is secured. Assuming that the back focus at the wide end is f _BW , f _BW = f ₃ (1−β _3W ). _Therefore , the larger the β _3W is, the larger the back focus is with respect to f ₃ determined by the equation (1). The lens diameter of the third group G3 can be reduced. When the magnification is larger than the upper limit of the expression (2), the overall length of the lens and the back focus are advantageous, but the combined power of the first group G1 and the second group G2 becomes too strong, and it is difficult to correct aberration fluctuation. Become.
If the magnification is smaller than the lower limit, the goal of miniaturization cannot be achieved.

Formula (3) is a conditional formula for reducing the lens diameter of the first lens unit G1. If the power of the first unit G1 is weaker than the upper limit of the expression (3), the entrance pupil position at the wide end becomes closer, which is advantageous in reducing the lens diameter of the first unit G1. Is too weak, which makes it difficult to correct aberration fluctuations, particularly curvature of field and distortion. In addition, the position of the entrance pupil at the tele (telephoto) end becomes far, and the overall length of the lens at the telephoto end becomes too large. Below the lower limit, the power of the first lens unit G1 becomes too strong, so that the goal of miniaturization cannot be achieved.

Next, even if the total length of the lens at the wide-angle end can be reduced by the formulas (1) and (2), the thickness of the camera body cannot be reduced when the movement amount due to zooming becomes large. . Therefore, in order to reduce the size, it is necessary to reduce the amount of movement of the group, and the conditional expression therefor is Expression (4). If the upper limit is exceeded, the power of each group becomes too weak, and the amount of movement increases. Conversely, if the lower limit is exceeded, the power of each group becomes too strong, making it difficult to correct aberrations.

Although the lens diameter of the first lens unit G1 can be reduced by the expression (3), the lens diameter can be reduced more optimally by defining the entrance pupil position by the expression (5). Can be achieved.

When the value exceeds the upper limit of the expression (5), the position of the entrance pupil becomes far, and the lens diameter of the first unit G1 becomes large. If the lower limit is exceeded, the entrance pupil position becomes closer, which is advantageous for reducing the lens diameter of the first group G1, but conversely, the lens diameter of the third group G3 increases and the off-axis position increases. It becomes difficult to correct aberration in

At the time of zooming from the wide-angle end to the telephoto end, an aperture stop is arranged in front of the second unit G2, and the second unit G2
And move it to the object side together. Thus, the entrance pupil distance can be shortened. If the aperture stop is disposed in the second group G2, eccentricity of the lens before and after the stop occurs, and the performance when the lens is assembled deteriorates. If the aperture stop is arranged on the rear side of the second group G2, the entrance pupil distance will increase.

Further, at the time of zooming, the first unit G1 and the third unit G
3 may be integrally moved to the object side. As a result, the lens frame structure of the lens can be simplified, and the diameter of the lens frame can be reduced and downsized. Further, the first group G1 and the third group G
3 has the effect of suppressing the occurrence of relative eccentricity.

By satisfying the conditional expressions (1) to (5), the lens diameter can be reduced. However, in order to correct aberrations more favorably, the lens configuration of each group is set as follows. It is desirable. The first group G1 includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. The second group G2 has at least one negative lens and at least two positive lenses. The third unit 3G includes at least two negative lenses. Further, the second group G2 is provided with at least one aspheric surface. The aspheric surface of the second group G2 has a shape in which the positive power gradually decreases as the distance from the optical axis increases, or the negative power gradually increases. Also, the second group G2
The negative lens and the positive lens can be joined or divided as necessary.

In the above lens configuration, when the average value of the refractive index of the d-line of the positive lens component in the second group G2 is <n _2p >, the following condition is satisfied: (6) <n _2p ><1.65 It is desirable. If the upper limit of the expression (6) is exceeded, the field curvature will be overcorrected, and it will be difficult to correct the curvature particularly on the wide side.

[0019]

Examples of the present invention will be described below. The lens data of Examples 1 to 8 will be described later, but FIG.
2 is a lens cross-sectional view at the wide-angle end (W) and the telephoto end (T), FIG. 2 is a lens cross-sectional view at the wide-angle end (W) of Examples 3, 5, 6, and 8, and FIG. Edge (W)
FIG. 4 shows a lens cross-sectional view of Example 7 at the wide-angle end (W).

In each of the eight embodiments, the first group G1 is composed of a cemented lens composed of a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side.

The second lens group G2 is composed of the negative meniscus lens, the positive lens, and the positive lens having the convex surface directed from the object side to the image side in the first and second embodiments. 5, 6, and 8 are composed of a negative meniscus lens having a convex surface facing the image side from the object side, a positive lens, and a cemented lens of a negative meniscus lens having a convex surface facing the object side and a positive lens. In Examples 4 and 7, the negative meniscus lens with the convex surface facing the image side, the positive meniscus lens with the convex surface facing the image side, and the cemented lens of the negative meniscus lens and the positive lens with the convex surface facing the object side from the object side. It is composed of four sheets.

Further, the third lens group G3 includes the first, second, and third embodiments.
5, 6, 7 and 8 are composed of a positive meniscus lens having a convex surface facing the image surface and a negative meniscus lens having a convex surface facing the image surface. From the object side, it is composed of a positive meniscus lens having a convex surface facing the image surface, a biconcave negative lens, and a negative meniscus lens having a convex surface facing the image surface.

With respect to the aspherical surface, in each of the embodiments except for the fourth embodiment, the last lens surface of the second lens unit G2 is used. In the fourth embodiment, the second lens unit of the second lens unit G2 is used.
It is used for one surface on the image side of the lens.

[0024] In the following, the symbols are as follows:
f is the focal length of the entire system, F _NO is the F number, 2ω is the angle of view,
f _B designates the back focal distance, r _1, r ₂ ... curvature radius of each lens surface, d _1, d ₂ ... the spacing between the lens surfaces, n _d1,
n _d2 ... is the refractive index of the d-line of each lens, v _d1 , v _d2 ... are the Abbe numbers of each lens, and the aspherical shape is x in the optical axis direction and y in the direction perpendicular to the optical axis. Then, it is expressed by the following equation.

X = (y ² / r) / [1+ {1-P (y ² / r ² )} ^1/2 ] + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰ r is the paraxial radius of curvature, P is the conic coefficient, A ₄ , A ₆ ,
A ₈ and A ₁₀ are aspherical coefficients.

[0026] Example _{1 f = 36.2 ~49.5 ~67.55 F NO} = 4.64 ~6.0 ~7.86 2ω = 61.7 ~47.2 ~35.5 ° f B = 7.0 ~17.118~30.713 r 1 = 13.4535 d 1 = 1.9349 n d1 = 1.80518 ν _d1 = 25.43 r ₂ = 10.4525 d ₂ = 2.7410 n _d2 = 1.48749 ν _d2 = 70.20 r ₃ = 21.0871 d ₃ = (variable) r ₄ = ∞ (aperture) d ₄ = 2.3438 r ₅ = -8.7803 d ₅ = 1.0580 n _d3 = 1.51742 ν _d3 = 52.41 r ₆ = -15.6134 d ₆ = 1.7311 r ₇ = 252.6154 d ₇ = 3.2268 nd ₄ = 1.48749 ν _d4 = 70.20 r ₈ = -12.5422 d ₈ = 0.2000 r ₉ = 84.0043 d ₉ = 1.9091 n _d5 = 1.56384 ν _d5 = 60.69 r ₁₀ = -50.4845 (aspherical surface) d ₁₀ = (variable) r ₁₁ = -17.7233 d ₁₁ = 2.2000 nd ₆ = 1.63980 ν _d6 = 34.48 r ₁₂ = -15.4587 d ₁₂ = 0.2000 r _{13 = -30.3087 d 13 = 1.4124 n d7} = 1.77250 ν d7 = 49.66 r 14 = -478.5832 d 14 = 3.5000 r 15 = -22.2136 d 15 = 1.7160 n d8 = 1.72916 ν d8 = 54.68 r 16 = -102.7414 zoom interval Aspheric coefficient 10th surface P = 1 A ₄ = 0.42867 × 10 ^-4 A ₆ = -0.27145 × 10 ^-7 A ₈ = 0.42421 × 10 ^-8 A ₁₀ = -0.57314 × 10 ^-10 | f ₃ / f _W | = 0.598 β _3W = 1.502 f ₁ / f _W = 2.487 f ₂ / f _W = 0.667 E _W / f _W = 0.225 <n _2p > = 1.53
.

[0027] Example _{2 f = 36.2 ~49.5 ~67.55 F NO} = 4.52 ~5.87 ~7.66 2ω = 61.7 ~47.2 ~35.5 ° f B = 7.0 ~17.109~30.691 r 1 = 13.6640 d 1 = 2.5185 n d1 = 1.80518 ν _d1 = 25.43 r ₂ = 10.1341 d ₂ = 3.0742 n _d2 = 1.48749 ν _d2 = 70.20 r ₃ = 21.3556 d ₃ = (variable) r ₄ = ∞ (aperture) d ₄ = 1.8000 r ₅ = -9.2733 d ₅ = 1.0463 n _d3 = 1.58904 ν _d3 = 53.20 r ₆ = -17.9885 d ₆ = 1.7850 r ₇ = 351.4614 d ₇ = 3.1310 n _d4 = 1.48749 ν _d4 = 70.20 r ₈ = -12.1155 d ₈ = 0.2000 r ₉ = 42.7990 d ₉ = 2.0333 n _{d5 = 1.56384 ν d5 = 60.69 r} 10 = -75.2257 ( aspherical) d ₁₀ = _{(variable) r 11 = -17.8272 d 11 =} 2.2000 n d6 = 1.65016 ν d6 = 39.39 r 12 = -14.6790 d 12 = 0.2000 r 13 _{= -30.6024 d 13 = 1.4000 n d7} = 1.75700 ν d7 = 47.87 r 14 = -317.2613 d 14 = 3.5000 r 15 = -18.7554 d 15 = 1.7000 n d8 = 1.71300 ν d8 = 53.84 r 16 = -83.4094 zoom interval Aspherical surface 10th surface P = 1 A ₄ = 0.47746 × 10 ^-4 A ₆ = 0.42452 × 10 ^-7 A ₈ = 0.55561 × 10 ^-9 A ₁₀ = -0.15989 × 10 ^-10 | f ₃ / f _W | = 0.607 β _3W = 1.480 f ₁ / f _W = 2.599 f ₂ / f _W = 0.659 E _W / f _W = 0.253 <n _2p > = 1.53
.

Example 3f = 36.2-49.5-67.55F
_NO = 4.65-6.0-7.9 2ω = 61.7-47.2-35.5
° f _B = 7.0 to 16.546 to 29.388 r ₁ = 12.8910 d ₁ = 1.6338 nd ₁ = 1.80518 ν _d1 = 25.43 r ₂ = 9.9680 d ₂ = 3.3742 nd ₂ = 1.48749 ν _d2 = 70.20 r ₃ = 20.7379 d ₃ = (variable ) r ₄ = ∞ _{(stop) d 4 = 1.8000 r 5 =} -10.9532 d 5 = 1.0000 n d3 = 1.58913 ν d3 = 60.97 r 6 = -32.2733 d 6 = 1.9483 r 7 = 301.7936 d 7 = 2.3000 n d4 = 1.63980 ν _d4 = 34.48 r ₈ = -18.2529 d ₈ = 0.5079 r ₉ = 31.8888 d ₉ = 1.0004 n _d5 = 1.80518 ν _d5 = 25.43 r ₁₀ = 15.0727 d ₁₀ = 4.2059 nd ₆ = 1.60729 ν _d6 = 59.38 r ₁₁ = -28.8720 (aspherical) d ₁₁ = _{(variable) r 12 = -15.9181 d 12 =} 2.3260 n d7 = 1.63980 ν d7 = 34.48 r 13 = -13.0578 d 13 = 0.2000 r 14 = -26.6001 d 14 = 1.4000 n d8 = 1.77250 ν _d8 = 49.66 r ₁₅ = -284.8814 d ₁₅ = 4.3000 r ₁₆ = -14.7071 d ₁₆ = 1.7000 _{nd 9} = 1.72916 ν _d9 = 54.68 r ₁₇ = -42.5091 Zoom interval Aspheric surface eleventh surface P = 1 A ₄ = 0.31972 × 10 ^-4 A ₆ = -0.25313 × 10 ^-7 A ₈ = 0.42076 × 10 ^-8 A ₁₀ = -0.43544 × 10 ^-10 | f ₃ / f _W | = 0.533 β _3W = 1.573 f ₁ / f _W = 2.314 f ₂ / f _W = 0.625 E _W / f _W = 0.237 <n _2p > = 1.62
.

[0029] Example _{4 f = 36.2 ~49.5 ~67.55 F NO} = 4.47 ~5.85 ~7.7 2ω = 61.7 ~47.2 ~35.5 ° f B = 7.0 ~17.075~30.653 r 1 = 13.4718 d 1 = 1.4979 n d1 = 1.80518 ν _d1 = 25.43 r ₂ = 10.6506 d ₂ = 2.7238 n _d2 = 1.48749 ν _d2 = 70.20 r ₃ = 20.1520 d ₃ = (variable) r ₄ = ∞ (aperture) d ₄ = 1.8000 r ₅ = -10.8115 d ₅ = 1.0000 n _d3 = 1.58913 ν _d3 = 60.97 r ₆ = -24.3782 d ₆ = 1.9453 r ₇ = -59.6460 d ₇ = 2.2517 nd ₄ = 1.63980 ν _d4 = 34.48 r ₈ = -18.0044 (aspherical surface) d ₈ = 0.1000 r ₉ = 40.4117 _{d 9 = 1.0004 n d5 = 1.80518} ν d5 = 25.43 r 10 = 18.5561 d 10 = 3.8955 n d6 = 1.60729 ν d6 = 59.38 r 11 = -21.3720 d 11 = ( _{variable) r 12 = -16.2680 d 12 =} 2.0194 n d7 _{= 1.63980 ν d7 = 34.48 r 13} = -14.0288 d 13 = 0.2000 r 14 = -48.3696 d 14 = 1.4000 n d8 = 1.77250 ν d8 = 49.66 r 15 = 296.6189 d 15 = 5.0000 r 16 = -14.3611 d 16 = 1.7000 n _d9 = 1.72916 ν _d9 = 54.68 r ₁₇ = -44.1027 Zoom interval Aspheric coefficient Eighth surface P = 1 A ₄ = 0.19134 × 10 ^-4 A ₆ = 0.30956 × 10 ^-6 A ₈ = 0.20235 × 10 ^-8 A ₁₀ = 0.21753 × 10 ^-9 | f ₃ / f _W | = 0.578 β _3W = 1.509 f ₁ / f _W = 2.813 f ₂ / f _W = 0.659 E _W / f _W = 0.210 <n _2p > = 1.62
.

[0030] Example _{5 f = 36.2 ~49.5 ~67.55 F NO} = 4.5 ~5.9 ~7.86 2ω = 61.7 ~47.2 ~35.5 ° f B = 7.0 ~17.473~31.617 r 1 = 13.6452 d 1 = 1.4695 n d1 = 1.80518 ν _d1 = 25.43 r ₂ = 10.8335 d ₂ = 2.5091 n _d2 = 1.48749 ν _d2 = 70.20 r ₃ = 18.9729 d ₃ = (variable) r ₄ = ∞ (aperture) d ₄ = 1.8000 r ₅ = -10.8293 d ₅ = 1.0000 n _d3 = 1.58913 ν _d3 = 60.97 r ₆ = -28.1982 d ₆ = 1.9787 r ₇ = 157.6300 d ₇ = 2.3351 n _d4 = 1.63980 ν _d4 = 34.48 r ₈ = -20.0441 d ₈ = 0.4943 r ₉ = 40.9546 d ₉ = 1.0004 n _d5 = 1.80518 ν _d5 = 25.43 r ₁₀ = 16.0579 d ₁₀ = 3.9815 n _d6 = 1.60729 ν _d6 = 59.38 r ₁₁ = -25.7306 (aspherical surface) d ₁₁ = (variable) r ₁₂ = -21.1326 d ₁₂ = 2.4384 n _d7 = _{1.63980 ν d7 = 34.48 r 13 =} -15.3146 d 13 = 0.2000 r 14 = -30.6754 d 14 = 1.4000 n d8 = 1.77250 ν d8 = 49.66 r 15 = -448.7953 d 15 = 4.6000 r 16 = -14.6285 d 16 = 1.7000 n _d9 = 1.72916 ν _d9 = 54.68 r ₁₇ = -43.8083 Zoom interval Aspheric coefficient Eleventh surface P = 1 A ₄ = 0.28521 × 10 ^-4 A ₆ = -0.11137 × 10 ^-6 A ₈ = 0.46633 × 10 ^-8 A ₁₀ = -0.55713 × 10 ^-10 | f ₃ / f _W | = 0.593 β _3W = 1.495 f ₁ / f _W = 3.462 f ₂ / f _W = 0.658 E _W / f _W = 0.201 <n _2p > = 1.62
.

[0031] Example _{6 f = 36.2 ~49.5 ~67.55 F NO} = 4.38 ~5.77 ~7.66 2ω = 61.7 ~47.2 ~35.5 ° f B = 7.0 ~19.383~36.11 r 1 = 14.8059 d 1 = 1.4347 n d1 = 1.80518 ν _d1 = 25.43 r ₂ = 12.0223 d ₂ = 2.1074 n _d2 = 1.48749 ν _d2 = 70.20 r ₃ = 19.2144 d ₃ = (variable) r ₄ = ∞ (aperture) d ₄ = 1.8000 r ₅ = -11.0194 d ₅ = 1.0000 n _d3 = 1.58913 ν _d3 = 60.97 r ₆ = -31.5905 d ₆ = 1.9743 r ₇ = 243.9211 d ₇ = 2.3140 n _d4 = 1.63980 ν _d4 = 34.48 r ₈ = -19.4003 d ₈ = 0.4429 r ₉ = 41.3266 d ₉ = 1.0004 n _d5 = 1.80518 ν _d5 = 25.43 r ₁₀ = 15.7095 d ₁₀ = 3.9784 n _d6 = 1.60729 ν _d6 = 59.38 r ₁₁ = -27.1220 (aspherical surface) d ₁₁ = (variable) r ₁₂ = -18.1028 d ₁₂ = 2.2001 n _d7 = _{1.63980 ν d7 = 34.48 r 13 =} -15.0688 d 13 = 0.2000 r 14 = -50.2245 d 14 = 1.4000 n d8 = 1.77250 ν d8 = 49.66 r 15 = -500.0000 d 15 = 5.0002 r 16 = -15.3428 d 16 = 1.7000 n _d9 = 1.72916 ν _d9 = 54.68 r ₁₇ = -41.7113 Zoom interval Aspheric coefficient Eleventh surface P = 1 A ₄ = 0.21893 × 10 ^-4 A ₆ = -0.14637 × 10 ^-6 A ₈ = 0.39041 × 10 ^-8 A ₁₀ = -0.41057 × 10 ^-10 | f ₃ / f _W | = 0.752 β _3W = 1.39 f ₁ / f _W = 4.705 f ₂ / f _W = 0.709 E _W / f _W = 0.186 <n _2p > = 1.62
.

[0032] Example _{7 f = 36.2 ~49.5 ~67.55 F NO} = 4.50 ~5.85 ~7.66 2ω = 61.7 ~47.2 ~35.5 ° f B = 7.39 ~16.48 ~28.704 r 1 = 13.1779 d 1 = 1.8330 n d1 = 1.80518 ν _d1 = 25.43 r ₂ = 9.9386 d ₂ = 3.9356 n _d2 = 1.48749 ν _d2 = 70.20 r ₃ = 22.3543 d ₃ = (variable) r ₄ = ∞ (aperture) d ₄ = 2.3446 r ₅ = -11.2947 d ₅ = 1.0000 n _d3 = 1.58913 ν _d3 = 60.97 r ₆ = -30.8349 d ₆ = 1.6015 r ₇ = -619.4777 d ₇ = 1.7692 n _d4 = 1.63980 ν _d4 = 34.48 r ₈ = -19.2825 d ₈ = 0.9317 r ₉ = 35.1756 d ₉ = 1.0000 n _d5 = 1.80518 ν _d5 = 25.43 r ₁₀ = 17.2468 d ₁₀ = 3.5688 nd ₆ = 1.60729 ν _d6 = 59.38 r ₁₁ = -23.2843 (aspheric) d ₁₁ = (variable) r ₁₂ = -18.5834 d ₁₂ = 2.5752 n _{d7 = 1.63980 ν d7 = 34.48 r 13} = -13.5522 d 13 = 0.2000 r 14 = -22.5824 d 14 = 1.0000 n d8 = 1.77250 ν d8 = 49.66 r 15 = -175.7960 d 15 = 4.0000 r 16 = -14.8727 d 16 = 1.0000 n _d9 = 1.72916 ν _d9 = 54.68 r ₁₇ = -49.7270 Zoom interval Aspheric coefficient Eleventh surface P = 1 A ₄ = 0.41618 × 10 ^-4 A ₆ = 0.66939 × 10 ^-8 A ₈ = 0.23548 × 10 ^-8 A ₁₀ = -0.93448 × 10 ^-11 | f ₃ / f _W | = 0.511 β _3W = 1.567 f ₁ / f _W = 2.217 f ₂ / f _W = 0.623 E _W / f _W = 0.246 <n _2p > = 1.62
.

[0033] Example _{8 f = 36.2 ~49.5 ~67.55 F NO} = 4.49 ~5.92 ~7.86 2ω = 61.7 ~47.2 ~35.5 ° f B = 7.0 ~17.712~32.187 r 1 = 13.7959 d 1 = 1.4666 n d1 = 1.80518 ν _d1 = 25.43 r ₂ = 10.9889 d ₂ = 2.5186 n _d2 = 1.48749 ν _d2 = 70.20 r ₃ = 18.6430 d ₃ = (variable) r ₄ = ∞ (aperture) d ₄ = 1.8000 r ₅ = -10.7884 d ₅ = 1.0000 n _d3 = 1.58913 ν _d3 = 60.97 r ₆ = -27.9676 d ₆ = 1.9813 r ₇ = 139.3309 d ₇ = 2.3392 n _d4 = 1.63980 ν _d4 = 34.48 r ₈ = -20.0662 d ₈ = 0.5012 r ₉ = 41.5458 d ₉ = 1.0004 n _{d5 = 1.80518 ν d5 = 25.43 r} 10 = 15.7488 d 10 = 3.9982 n d6 = 1.60729 ν d6 = 59.38 r 11 = -25.8684 ( aspherical) d ₁₁ = _{(variable) r 12 = -22.3919 d 12 =} 2.6169 n d7 = _{1.63980 ν d7 = 34.48 r 13 =} -15.3974 d 13 = 0.2000 r 14 = -30.5013 d 14 = 1.4000 n d8 = 1.77250 ν d8 = 49.66 r 15 = -448.7953 d 15 = 4.6000 r 16 = -14.4370 d 16 = 1.7000 n _d9 = 1.72916 ν _d9 = 54.68 r ₁₇ = -42.7598 Zoom interval Aspheric surface eleventh surface P = 1 A ₄ = 0.28523 × 10 ^-4 A ₆ = -0.10242 × 10 ^-6 A ₈ = 0.43313 × 10 ^-8 A ₁₀ = -0.53557 × 10 ^-10 | f ₃ / f _W | = 0.610 β _3W = 1.478 f ₁ / f _W = 3.794 f ₂ / f _W = 0.661 E _W / f _W = 0.201 <n _2p > = 1.62
.

The wide end (W) of each of the first to eighth embodiments,
FIGS. 5 to 12 show aberration diagrams in the standard state (S) and the telephoto end (T), respectively.

[0035]

The compact three-unit zoom lens according to the present invention is a zoom lens having a zoom ratio of about 2, the telephoto ratio at the wide end is as short as 1.3 or less, and the lens diameter of the first group is small. Thus, a small lens having a short lens length can be obtained.
This zoom lens is suitable for a lens shutter camera or the like.

[Brief description of the drawings]

FIG. 1 shows a wide end (W) and a telephoto end (T) of Examples 1 and 2.
It is a lens sectional view in.

FIG. 2 is a lens cross-sectional view at a wide end (W) of Examples 3, 5, 6, and 8;

FIG. 3 is a lens cross-sectional view at a wide end (W) according to a fourth embodiment.

FIG. 4 is a lens cross-sectional view at a wide end (W) according to a seventh embodiment.

FIG. 5 is an aberration diagram at a wide end (W), a standard state (S), and a telephoto end (T) according to the first embodiment.

FIG. 6 is an aberration diagram similar to FIG. 5 of the second embodiment.

FIG. 7 is an aberration diagram similar to FIG. 5 of the third embodiment.

FIG. 8 is an aberration diagram similar to FIG. 5 of the fourth embodiment.

FIG. 9 is an aberration diagram similar to FIG. 5 of the fifth embodiment.

FIG. 10 is an aberration diagram similar to FIG. 5 of the sixth embodiment.

FIG. 11 is an aberration diagram similar to FIG. 5 in the seventh embodiment.

FIG. 12 is an aberration diagram similar to FIG. 5 of the eighth embodiment.

[Explanation of symbols]

 G1 first group G2 second group G3 third group

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (8)

(57) [Claims] 1. A first lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power, which are arranged in order from the object side. A three-unit zoom lens in which a first unit and a third unit move to the object side, and a second unit moves to the object side at a relatively slow speed relative to them, and the following conditional expressions (1) to ( 5 ) (1) 0.5 <| f ₃ / f _W | <0.9 (2) 1.3 <β _3W <2.0 (3) 1 0.7 <f ₁ / f _W <5.0 (4) 0.5 <f ₂ / f _W <1.3 (5) 0.1 <E _W / f _W ≦ 0.237 where f _W is a wide angle The focal length of the whole system at the edge, f ₁ ,
f ₂ and f ₃ are the focal lengths of the first, second, and third groups, respectively, β _3W is the imaging magnification of the third group at the wide-angle end , and E _W is wide.
This is the distance from the first lens surface to the entrance pupil position at the corner end . 2. An aperture stop is arranged in front of the second group,
Wherein upon zooming from the wide-angle end to the telephoto end, the aperture stop is the second group and a small three-unit zoom lens according to claim 1, wherein the integral that is configured to move toward the object side. 3. The small-sized camera according to claim 1, wherein the first unit and the third unit are integrally moved to the object side during zooming from the wide-angle end to the telephoto end. 3 group zoom lens. 4. The first group includes a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side, and the second group has at least one negative lens. The small three-unit zoom lens according to claim 1, wherein the third unit includes at least two positive lenses, and the third unit includes at least two negative lenses. 5. The small three-group zoom lens according to claim 4, wherein at least one aspherical surface is provided in said second group. 6. The aspheric surface according to claim 1, wherein the positive power gradually decreases as the distance from the optical axis increases, or the negative power gradually increases. 5. A compact three-group zoom lens according to 5. 7. The compact three-unit zoom lens according to claim 4, wherein the negative lens and the positive lens of the second group are constituted by cemented lenses. 8. When the average value of the refractive index of the d-line of the positive lens component in the second group is set to <n _2p >, the following conditional expression (6) is satisfied. claims 1 to 7 or one of claims small three-unit zoom _{lens: (6) <n 2p>} <1.65